Rest api conventions

Skill rrezartprebreza/spring-boot-skills/skills/spring-boot-3/rest-api-conventions

Production-grade Claude Code and Codex skills for Spring Boot developers

Install

npx -y skills add rrezartprebreza/spring-boot-skills --skill rest-api-conventions

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

What its author says it does

Copied from the file, not written here

Use when generating REST controllers, response wrappers, DTOs, error handlers, or any HTTP-facing code. Defines response envelope, HTTP status mapping, pagination, and versioning.

SKILL.md

4.7 KB, as published. Nobody here has run it

REST API Conventions

Response Envelope

All endpoints return a consistent envelope:

{
  "success": true,
  "data": { },
  "error": null,
  "timestamp": "2026-04-13T10:00:00Z"
}

Error response:

{
  "success": false,
  "data": null,
  "error": {
    "code": "ORDER_NOT_FOUND",
    "message": "Order with id 123 not found",
    "details": []
  },
  "timestamp": "2026-04-13T10:00:00Z"
}

ApiResponse Wrapper

@JsonInclude(JsonInclude.Include.NON_NULL)
public record ApiResponse<T>(
    boolean success,
    T data,
    ApiError error,
    Instant timestamp
) {
    public static <T> ApiResponse<T> ok(T data) {
        return new ApiResponse<>(true, data, null, Instant.now());
    }

    public static <T> ApiResponse<T> error(String code, String message) {
        return new ApiResponse<>(false, null, new ApiError(code, message, List.of()), Instant.now());
    }
}

public record ApiError(String code, String message, List<String> details) {}

HTTP Status Mapping

Scenario	Status
GET — found	200
POST — created resource	201
PUT/PATCH — updated	200
DELETE — deleted	204 (no body)
Validation failure	400
Unauthenticated	401
Forbidden	403
Not found	404
Conflict (duplicate)	409
Unhandled server error	500

URL Conventions

Plural nouns for resources: /orders, /users, /products
Kebab-case for multi-word: /order-items, not /orderItems
Versioning in path: /api/v1/orders
Nested resources max 2 levels: /orders/{id}/items ✅, /orders/{id}/items/{itemId}/notes ❌ — flatten to /order-item-notes/{id}
IDs as UUIDs in path, never auto-increment integers exposed in URL

GET    /api/v1/orders              → list (paginated)
POST   /api/v1/orders              → create
GET    /api/v1/orders/{id}         → get one
PUT    /api/v1/orders/{id}         → full update
PATCH  /api/v1/orders/{id}         → partial update
DELETE /api/v1/orders/{id}         → delete
GET    /api/v1/orders/{id}/items   → nested resource

Pagination

{
  "success": true,
  "data": {
    "content": [...],
    "page": 0,
    "size": 20,
    "totalElements": 150,
    "totalPages": 8,
    "last": false
  }
}

Query params: ?page=0&size=20&sort=createdAt,desc

Use Spring Data Pageable in controllers:

@GetMapping
public ApiResponse<Page<OrderResponse>> list(Pageable pageable) {
    return ApiResponse.ok(orderService.findAll(pageable).map(OrderResponse::from));
}

Cap the page size. A bare Pageable accepts ?size=100000 from any client — one request can drag your whole table into memory. Spring's default cap is 2000, still too high for most APIs:

spring:
  data:
    web:
      pageable:
        default-page-size: 20
        max-page-size: 100   # requests above this are silently clamped

Global Exception Handler

@RestControllerAdvice
@RequiredArgsConstructor
public class GlobalExceptionHandler {

    @ExceptionHandler(EntityNotFoundException.class)
    public ResponseEntity<ApiResponse<Void>> handleNotFound(EntityNotFoundException ex) {
        return ResponseEntity.status(404).body(ApiResponse.error("NOT_FOUND", ex.getMessage()));
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ApiResponse<Void>> handleValidation(MethodArgumentNotValidException ex) {
        List<String> details = ex.getBindingResult().getFieldErrors().stream()
            .map(e -> e.getField() + ": " + e.getDefaultMessage()).toList();
        return ResponseEntity.status(400)
            .body(new ApiResponse<>(false, null, new ApiError("VALIDATION_FAILED", "Invalid input", details), Instant.now()));
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ApiResponse<Void>> handleGeneric(Exception ex) {
        return ResponseEntity.status(500).body(ApiResponse.error("INTERNAL_ERROR", "An unexpected error occurred"));
    }
}

Gotchas

Agent returns raw objects without envelope — always wrap in ApiResponse.ok(...)
Agent uses ResponseEntity<Map<String, Object>> for errors — use ApiResponse
Agent puts exception handlers in controllers — always use @RestControllerAdvice
Agent uses Long IDs in URLs — use UUID
Agent accepts unbounded Pageable — set spring.data.web.pageable.max-page-size or one request can pull the whole table
Agent returns Page<Entity> serialized directly — exposes Hibernate internals; map to DTOs first